The present invention relates to hitch structures for a semiintegrally integrtally mounting a power take-off (PTO) driven implement to a tractor three-point hitch and more specifically relates to hitch adapters embodied in such structures.
When a PTO-driven implement is semi-integrally mounted to the three-point hitch of a tractor, the power shaft coupling the tractor PTO shaft to the implement transmission extends beneath the upper link of the three-point hitch. In the past, such hitch arrangements have had the disadvantage that interference between the power shaft and the upper link of, or a quick coupler carried by, the three-point hitch could result when the hitch approached the lower extreme of its movement
In U.S. Pat. Nos. 4,366,877 and 4,525,987, this problem is avoided by using a hitch arrangement which eliminates the upper link of the three-point hitch and avoids the use of other structure located in the area above the power shaft. This solution to the problem is not entirely satisfactory, however, since the elimination of the top link for support results in increased bending moments being induced in the structure, in this case the implement drive housing, coupled to the three-point hitch lower links.
In co-pending U.S. patent application Ser. No. 927,467 filed 6 November 1986, which application was continued as application Ser. No. 088,501 filed Aug. 19, 1987 that issued as U.S. Pat. No. 4,738,461 on Apr. 19, 1988, the problem is avoided, in a structure including a hitch adapter carried at the rear of a three-point hitch and having a drawbar coupled to the implement tongue, by providing the hitch adapter with a stop bar that engages the tractor drawbar to prevent the three-point hitch from lowering beyond a predetermined point. This structure is effective to prevent interference between the three-point hitch and the power shaft but has the disadvantage that the stop bar makes it difficult to lower the three-point hitch to disengage a quick coupler from the hitch adapter.